Containers such as bottles and cans for the retention of liquid under pressure of the type used for carbonated beverages, beer, and the like have usually been blow-molded from extruded parisons without much improvement in mechanical strength in the axial direction resulting from orientation due to the fact the article was not significantly axially stretched and the temperature at which stretching occurred was too high. More recently, as set forth in U.S. Pat. No. 3,949,033, there have been proposals to preform an initially freely extruded parison to an intermediate closed bottom parison prior to finally blowing it to the desired physical configuration with air under pressure in the usual manner. In the patent mentioned, another embodiment of the invention uses an injection molded parison instead of an initially extruded parison and in both instances the final step in the process is a mechanical reforming of the closed container bottom to achieve an enhanced bottom strength in the container.
In another U.S. Pat. No. 3,461,503, a container is formed from a parison having a press molded neck by stretching the closed bottom of the parison and then radially blow stretching it while leaving the neck portion of the bottle in its original state, so that the neck portion of the bottle is considerably thicker than the relatively thin-walled body. This process was proposed to overcome a disadvantage heretofore present when widemouth containers were formed with neck portions of inadequate strength and rigidity.
U.S. Pat. No. 3,896,200 is directed to a method of bi-axially orienting a blow-molded article by providing a parison shorter than a mold into which it is placed and stretching the parison axially. Other, usually bi-axially oriented containers are disclosed in U.S. Pat. Nos. 3,170,971, 3,303,249, 3,784,342, 3,865,530, 4,017,250, 4,151,250 and 4,155,697, but in each instance, the containers are formed in one piece and do not have the axial rigidity of containers formed in accordance with the present invention. Where methods of the character disclosed in the aforementioned patents produce some beneficial rigidity and strength characteristics as a result of the bi-axial orientation of the container or bottle, the method which I will disclose provides greatly improved strength and rigidity characteristics in containers which I form of multiple container sections.
One of the prime objects of the invention is to provide a bi-axially oriented bottle or container with enhanced axial strength and rigidity in comparison to bottles or containers being presently formed by known blow-molding technology.
Another object of the invention is to provide a high production rate method of forming such containers which permits making them at considerably greater speeds than formerly, with the economies inherent in increased production per unit of time.
Still a further object of the invention is to provide an improved method of forming containers of the character described, which is extremely reliable in terms of the manufacture of leak-proof containers, while still providing the containers at considerably decreased cost.